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tÉlÉcharger laser torch based voice transmitter and receiver full report pdf

Advanced Science and Technology Letters
Vol.30 (ICCA 2013), pp.203-210
Wireless Laser Torch-Based Voice Transmitter and
Debnath Bhattacharyya1*, Bijoy Kumar Manadal1, Suntae Kim2
Department of Computer Science and Engineering,
Faculty of Engineering and Technology,
NSHM Knowledge Campus – Durgapur,
Durgapur-713212, India.
[email protected], [email protected]
Department of Computer Engineering, Kangwon National University,
Kangwon-Province, South Korea
Corresponding Author: [email protected]
Abstract. In this paper we designed the circuit, using that circuit we can
communicate with our neighbors wirelessly. Instead of RF signals, light from a
laser torch is used as the carrier in the circuit. The laser torch can transmit light
up to a distance of about 500 meters. The phototransistor of the receiver must
be accurately oriented towards the laser beam from the torch. If there is any
obstruction in the path of the laser beam, no sound will be heard from the
receiver. The transmitter circuit comprises condenser microphone transistor
amplifier BC548 followed by an pomp stage built around µA741. The gain of
the op-amp can be controlled with the help of 1-mega-ohm potmeter VR1.The
AF output from IC1 is coupled to the base of transistor BD139 (T2), which, in
turn, modulates the laser beam. The transmitter uses 9V power supply.
However, the 3-volt laser torch (after removal of its battery) can be directly
connected to the circuit²with the body of The torch connected to the emitter of
BD139 and the spring-loaded lead protruding from inside the torch to circuit
ground. The receiver circuit uses an NPN phototransistor as the light sensor
that is followed by a two-stage transistor preamplifier and LM386-based audio
Power amplifier. The receiver does not need any complicated alignment. Just
keep the phototransistor oriented towards the remote transmitters laser point
and adjust The volume control for a clear sound To avoid 50Hz hum noise in
the speaker, keep the phototransistor away from AC light sources such as bulbs.
The reflected sunlight, however, does not cause any problem. But the sensor
should not directly face the sun.
Keywords: Laser, LST, RF, LM386, Wireless.
1 Introduction
Laser as a communication medium can provide a good substitute for the present day
communication systems as the problem of interference faced in case of
electromagnetic waves is not there and high deal of secrecy is available. It will easily
ISSN: 2287-1233 ASTL
Copyright 2013 SERSC
Advanced Science and Technology Letters
Vol.30 (ICCA 2013)
give a communication distance of several hundred meters, and with a parabolic light
reflector, up to several kilometers [1]. The laser-induced lubricant pockets generated
high local pressures and thus caused a thicker lubricant film, allowing an optimal
separation of the contact surfaces even at lower sliding velocities [2]. It transmits
high quality audio and the link is virtually impossible for anyone else to tap into. An
important feature of transmission by laser beam is privacy. Because a laser beam is
intentionally narrow, it's virtually impossible for someone to tap into the link without
us knowing. If someone intercepts the beam, the link is broken, signaling the
interception. Fibre-optic cables also have high security, as it's very difficult to splice
into the cable without breaking the link. However it's theoretically possible; so for
the highest security, we probably cannot beat a line-of-sight laser beam. Also it
cannot be detected with use of spectrum analyzers and RF meters and hence can be
used for diverse applications including financial, medical and military. Laser Surface
Texturing (LST) is probably the most advanced so far. LST produces a very large
number of micro-dimples on the surface and each of these micro-dimples can serve
either as a micro-hydrodynamic bearing in cases of full or mixed lubrication, a microreservoir for lubricant in cases of starved lubrication conditions, or a micro-trap for
wear debris in either lubricated or dry sliding [3]. Lasers can also transmit through
glass; however the physical properties of the glass have to be considered. By rotating
the media under the focused pulsed‐laser beam, a row of crater shaped dimples are
created in the landing zone only [4]. Laser transmitter and receiver units ensure easy,
straightforward systems alignment and long-term stable, service free operation,
especially in inaccessible environments, optical wireless systems offer ideal,
economical alternative to expensive leased lines for buildings [5, 7]. Over the past 10
Years, laser intensities have increased by more than four orders of magnitude to
reach enormous intensities of 1020 W /cm2 [6].The laser can also be commissioned
in satellites for communication, as laser radar requires small aperture as compared to
microwave radar. As we cannot see the laser beam without special IR sensitive
equipment, it also makes alignment more difficult. Further, potential bandwidth of
radar using lasers can translate to very precision range measurement. For these
reasons, they can be used as an alternative to present modes of communication. Laser
communication is both wide-band and high-speed.
Design Of Working Principle
The block diagram of working principle of the system is shown in Figure 1.
Fig.1. Block Diagram of Working Principle of System.
Copyright © 2013 SERSC
Advanced Science and Technology Letters
Vol.30 (ICCA 2013)
A) Condenser Microphone
Condenser microphones require power from a battery or external source. Condenser
also tends to be more sensitive and responsive than dynamic, making them well suited
to capturing subtle nuances in a sound. The diaphragm vibrates when struck by sound
waves, changing the distance between the two plates and therefore changing the
capacitance. Specifically when the plates are closer together capacitance increases and
a charge current occurs and this current will be used to trigger the transmitting section.
B) Transmitting Section
The transmitter section comprises condenser microphone, transistor amplifier BC548
followed by an op-amp stage built around IC1. The gain of the op-amp can be
controlled with the help of 1-mega ohm pot meter VR1. The AF output from IC1 is
coupled to the base of transistor Bd139, which in turn, modulates the laser beam. The
transmitter uses 9V power supply. However, the 3-volt laser torch (after the removal